A boiler in a thermal power generation plant is a typical example of conventional combustion furnaces. Most boilers used there are coal burning boilers whose fuel is pulverized coal or petroleum burning boilers whose fuel is petroleum.
In the coal burning boiler, pulverized coal made by pulverizing coal is charged into a combustion furnace via a pulverized coal supply pipe of a pulverized coal burner using a transport gas. While, a combustion air is charged also into the combustion furnace through a path around the pulverized coal supply pipe. Note that, since a compressed air is normally used as a transport gas for transporting the pulverized coal, the compressed air also contributes to combustion in the combustion furnace.
In the pulverized coal burner, an air flow influencing portion (swirler and rib described later) for influencing air flow is normally provided inside a tip end side part of the pulverized coal supply pipe for improving ignition/flame stability of the pulverized coal burner. By providing the air flow influencing portion inside the tip end of the pulverized coal supply pipe in this manner, the pulverized coal can be dispersed and supplied into the combustion furnace and also a relatively large reverse-flow region can be generated in the combustion furnace.
As a conventional example of the air flow influencing portion in the pulverized coal burner, in Patent document 1 for example, a turn degree adjustment blade (rib) 42 is provided inside a tip end of a pulverized coal supply pipe 41 of a pulverized coal burner 40, as illustrated in FIG. 13. Additionally, in this example, a turning blade 43 is provided in the midway of a flow passage of the pulverized coal supply pipe 41.
In the conventional example illustrated in FIG. 13, firstly a turning component applied to the pulverized coal/transport air 44 flowing into the pulverized coal supply pipe 41 by the turning blade 43. The pulverized coal/transport air 44 to which the turning component has been applied is decreased in turn degree by the turn degree adjustment blade (rib) 42 provided inside the tip end of the pulverized coal supply pipe 41, and charged into a combustion furnace 45 after being adjusted in turn degree.
If flow velocity of the pulverized coal/transport air 44 supplied from the pulverized coal supply pipe 41 into the combustion furnace 45 is too fast, the pulverized coal becomes hard to combust in the combustion furnace 45. In this regard, since the turn degree of the pulverized coal/transport air 44 charged into the combustion furnace 45 is adjusted by the turn degree adjustment blade 42 in the conventional example illustrated in FIG. 13, the velocity of the pulverized coal/transport air 44 is decreased and the ignition/flame stability of the pulverized coal can be improved.
Additionally, as another conventional example, Patent document 2 also describes a configuration in which a swirler for turning pulverized coal (turning blade) is provided inside a tip end of a primary throat for transporting the pulverized coal using a transport air.
By the way, although the pulverized coal and petroleum are typical examples of fuel for the combustion furnace such as a boiler as mentioned above, petroleum pitch (petroleum residue) is often used as fuel instead. Of the petroleum pitch, heavy one is a solid fuel as the pulverized coal, and even when the solid petroleum pitch is used as fuel, the basic structure of the boiler is not significantly different from that of the coal burning boiler.